The present invention relates to an engine testing apparatus.
As an apparatus for checking performance of an automobile engine, there exists an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The engine testing apparatus controls the dynamo controller and the actuator to adjust the output of the engine under test.
FIG. 3 schematically shows a general structure of the engine testing apparatus. In FIG. 3, reference numeral 1 represents an engine under test and reference numeral 2 represents a dynamometer. An output shaft 1a of the engine 1 and a driving shaft 2a of the dynamometer 2 are coupled to each other through a clutch 3 such that the shafts 1a and 2a can be connected to and disconnected from each other. Reference numeral 4 represents a clutch actuator for driving the clutch 3. Reference numeral 5 represents a throttle of the engine 1 under test, and the throttle 5 is driven by a throttle actuator 6 and its throttle opening degree is controlled. Reference numeral 7 represents a dynamo controller for controlling the dynamometer 2. Reference numeral 8 represents a torque sensor mounted to the driving shaft 2a of the dynamometer 2, and reference numeral 9 represents a torque amplifier for appropriately amplifying the output of the torque sensor 8.
Reference numeral 10 represents a control computer as a simulator for controlling the entire apparatus, and reference numeral 11 represents a signal conditioner unit. The computer 10 performs a computation based on an input from an input apparatus (not shown) and based on signals from various sensors such as the torque sensor 8 provided in the apparatus, and outputs commands to various portions of the apparatus. For example, a target vehicle speed pattern 12 shown in FIG. 3, a target vehicle speed pattern 12a shown in FIG. 4(A) or a target vehicle speed pattern 12b shown in FIGS. 2 and 6 are inputted to the computer 10. That is, in each of the target vehicle speed patterns 12, 12a and 12b, the horizontal axis shows time (second) and vertical axis shows speed (km/h), and these patterns are target running patterns of desired driving.
The signal conditioner unit 11 is an interface having an AD converting function and a DA converting function. The AD converting function of the signal conditioner unit 11 converts signals from various sensors such as a torque sensor 8. The DA converting function converts commands from the computer 10, and output commands to various portion of the apparatus such as the dynamo controller 7, the clutch actuator 4 and the throttle actuator 6.
In a conventional engine testing apparatus, as shown in FIGS. 5 and 9, the moment of inertia of the engine is used to compute the load of rotating objects of an actual vehicle, i.e., an engine, a transmission, a differential gear and tire. This is because the moment of inertia of the engine is greater than moments of other rotating objects.
FIGS. 5 and 9 respectively show a conventional control flow and computation flow for the above-described engine testing apparatus. First, the control flow is described. In FIG. 5, reference numeral 13 represents a target pattern generator. The target pattern generator 13, which is provided in the computer 10, outputs a target speed signal V, to allow the engine 1 under test to run in a predetermined running pattern based on the target vehicle speed patterns 12, 12a and 12b which have been inputted into the computer 10. The target speed signal V, is inputted to a rotation control system 14 and a simulation vehicle control system 15.
The rotation control system 14 and the simulation vehicle control system 15 are constituted in the following manner. First, the rotation control system 14 comprises a rotation generator 16 to which the target speed signal V, is inputted, a delay correcting circuit 17, a butt portion 18, a rotation feedback controller 19 and the dynamometer 2. When the target speed signal Vr is inputted to the rotation generator 16, an engine target rotation number signal [a target value of the dynamometer rotation number (the rotation number, hereinafter)] Rr is outputted from the rotation generator 16 based on the target speed signal Vr.
For example, as shown in FIG. 4(B), a target rotation number signal Rr which is converted from the target vehicle speed pattern 12a shown in FIG. 4(A) is obtained in simulation. That is, an engine rotation pattern 33 is obtained. Similarly, when the target vehicle pattern 12b, is employed, an engine rotation pattern 30, which is converted from the target vehicle speed pattern 12b is obtained as shown in FIG. 6. When the pattern is converted from target vehicle speed pattern 12a to the engine rotation pattern 33 or from the target vehicle speed pattern 12b to the engine rotation pattern 30, a diameter of a tire, a final-drive ratio and a gear ratio in accordance the type of vehicle are taken into consideration.
Referring back to FIG. 5, the target rotation number signal Rr becomes a control target rotation number signal Rctl through the delay correcting circuit 17, and is outputted to the butt point 18. Since an actual rotation number signal Ra of the dynamometer 2 has been inputted to the butt point 18, a deviation Re between the control target rotation number signal Rctl and an actual rotation number signal Ra is PI-controlled, for example, by the rotation feedback controller 19, thereby setting an operation amount signal Udxe2x80x2. The operation amount signal Udxe2x80x2 is sent to the dynamometer 2.
In FIG. 5, the simulation vehicle control system 15 includes a torque generator 20 to which the target speed signal Vr is inputted and further includes a butt point 21 to which the target speed Vr is inputted and a speed feedback controller 22 are connected in parallel to a rear stage of the target pattern generator 13 which outputs the target speed signal Vr. A torque control system 27, which comprises an adding point 23, a butt point 24, a throttle map 25, a throttle opening degree controller 26 and the engine 1 under test, is provided in the rear stage of the torque generator 20 and the speed feedback controller 22. A simulation vehicle model 28 is provided in the rear stage of the torque control system 27. The throttle map 25 is a map for determining a target throttle opening degree to control the engine. The simulation vehicle model 28 is a model for calculating a driving force of the vehicle using the engine output torque to convert the calculated value into a speed signal using the driving force.
In the simulation vehicle control system 15, if the target speed Vr is inputted to the torque generator 20, a feedforward torque Tff, which is an output torque required for the engine from the torque generator 20, is outputted to the adding point 23. In this case, when the target vehicle speed pattern 12 or the target vehicle speed patterns 12a and 12b is converted into the feedforward torque Tff, a vehicle inertia weight and running resistance in accordance with the type of vehicle are taken into consideration.
The target speed signal Vr is butted against an actual speed signal Va outputted from the simulation vehicle model 28 at the butt point 21. A deviation there between is sent to the speed feedback controller 22, and it is outputted to the adding point 23 as a feedback torque Tfb. The feedforward torque Tff and the feedback torque Tfb are added in the adding point 23, and the target control torque signal Tctl is obtained. The target control torque signal Tctl is butted against an actual output torque valve Ta of the engine 1 under test, a deviation Te thereof is inputted to the throttle map 25. An operation target throttle opening degree xcex8 is obtained. The operation target throttle opening degree xcex8 is input to the throttle opening degree controller 26, an operation amount Ua is set, and the operation amount signal Ua is sent to the engine under test 1.
Next, the computation flow is explained. In FIG. 9, reference numerals 49 and 50 respectively represent a torque computation system and a rotation computation system. The torque computation system 49 comprises a butt point 51 for butting the output torque value Ta of the engine 1 under test and a torque value TE resulting from an engine inertia moment Je against each other, a multiplier 52 for multiplying the output T1 of the butt point 51 by a gear charge ratio Gr and for outputting a torque value T2 after gear change, a multiplier 53 for multiplying the torque value T2 after gear change by a differential gear ratio Gf and for outputting a torque value T3 through the differential gear, and a multiplier 54 for multiplying the torque value T3 through the differential gear by reciprocal 1/R of a tire diameter R and outputting a driving force Fvehicle of a tire surface.
The rotation computation system 50 comprises a multiplier 56 for multiplying a target vehicle speed Vvehicle by a tire slip ratio k from a calculator 55, which obtains the tire slip ratio k, and for outputting the target vehicle speed Vtar after correction of slip ratio, a multiplier 57 for multiplying the target vehicle speed Vtar by a multiplier (1/2xcfx80R) concerning the tire diameter and for outputting a rotation angle speed n1 of the tire, a multiplier 58 for multiplying the rotation angle speed n1 of the tire by a multiplier (1/Gf) concerning the gear ratio and for obtaining a rotation angle speed n2 closer to an entrance of the differential gear (closer to the engine), and a multiplier 59 for multiplying the rotation angle speed n2 closer to the entrance of the differential gear by a multiplier (1/Gr) concerning the gear change ratio and for obtaining an engine rotation angle speed n3 (corresponding to the Vr).
Reference numeral 60 represents a differentiator for differentiating the engine rotation angle speed n3 and for outputting an engine rotation acceleration xcfx89e and reference numeral 61 represents a multiplier for multiplying the engine rotation acceleration xcfx89e by an engine inertia moment Je and for outputting a torque value Te caused by engine inertia. The torque value Te caused by engine inertia is outputted to a butt point 51 of the torque computation system 49.
In the above-described conventional engine testing apparatus, a single transmission efficiency constant, which concerns a transmission of engine output to a road surface and a driving force which accelerates the vehicle, is utilized. That is the transmission efficiency constant matches the rotation number of a roller for 2-shaft chassis dynamo with the rotation number of an actual vehicle where constant speed (normal) driving is presumed.
However, tire slippage occurs on the road surface under actual operating conditions (actual running vehicle in actual case). That is, in the conventional engine testing apparatus, as markedly shown in the 2-shaft chassis dynamo, it is impossible to reproduce the change of the slip ratio between the tire and the roller related to the difference in the tire deformation degree of the tire at the time of constant speed running, acceleration running and deceleration running.
To sum up, slip is not simulated in the conventional engine testing apparatus shown in FIG. 6. For simulation conducted by the conventional testing apparatus, a difference is generated between the engine rotation pattern 30 converted from the target vehicle speed pattern 12b and the engine rotation pattern 31 measured when the actual vehicle runs on a chassis dynamo. It can be found from FIG. 6 that the engine rotation pattern 30 is shifted lower than the engine rotation pattern 31 at the time of acceleration and shifted higher than the engine rotation pattern 31 at the time of deceleration.
In order to reproduce the engine rotation of the actual vehicle running, it is necessary to consider the slippage between the tire and road surface in addition to the tire diameter, the final-drive ratio, the gear ratio and the vehicle inertia weight. However, in the case of the conventional engine testing apparatus, this point is lacking and therefore, an accurate simulation can not be conducted.
A first invention has been accomplished in view of the above circumstances, and an object of the first invention is to provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle.
In the above-described conventional engine testing apparatus, as shown in FIGS. 5 and 9, the rotational acceleration of the engine 1 under test obtained in the rotation computation system 50 is multiplied by an inertia moment of the engine 1 under test, and the result is used in the torque computation in the torque computation system 49 to calculate a load. That is, the simulation is conducted such that at the time of acceleration, the output torque TE corresponding to the inertia of the engine 1 under test is absorbed by the dynamometer 2, and at the time of deceleration, the torque is increased on the contrary.
However, in the actual vehicle running in the actual case, inertia of other rotating bodies such as the transmission, a differential gear and a tire exert an influence upon the load, and in the case of the conventional engine testing apparatus, this consideration is lacking and thus, an accurate simulation can not be conducted.
A second invention has been accomplished in view of the above-described circumstances, and an object of the second invention is provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle.
Since a rotational driving force of the engine through the transmission and differential gear is transmitted to the tire at a ratio of 1:1, it is conceivable that controlling the actual rotation number Ra of the dynamometer 2 is the same as controlling the rotation number of the engine in effect. From this point of view, in the engine testing apparatus, it is necessary to reproduce the rotation number of the engine in the actual running vehicle.
However, in the actual running vehicle in the actual case, tire slippage occurs on the road surface. The conventional engine testing apparatus does not take this slippage into consideration, i.e., tire slippage is not simulated. Thus, as shown in FIG. 6, in a simulation carried out in the conventional engine testing apparatus, a difference is generated between the engine rotation pattern 30 converted from the target vehicle speed pattern 12b and the engine rotation pattern 31 measured when the actual vehicle runs on a chassis dynamo. It can be found from FIG. 6 that the engine rotation pattern 30 is shifted lower than the engine rotation pattern 31 at the time of acceleration and shifted higher than the engine rotation pattern 31 at the time of deceleration.
To sum up, in order to reproduce the engine rotation of the actual running vehicle, it is necessary to take into consideration tire slippage between the tire and road surface in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance. However, in the case of the conventional engine testing apparatus, this point is lacking and therefore, an accurate simulation can not be conducted.
A third invention has been accomplished in view of the above circumstances, and an object of the third invention is to provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle.
To achieve the above object, according to the first invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test for simulating an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein a constant speed driving slip ratio (Sa) in a constant speed running state for a target vehicle speed pattern, an acceleration driving slip ratio (Sb) in an acceleration running state, and a deceleration driving slip ratio (Sc) in a deceleration running state are previously computed and stored as data for correcting tire slippage during the actual vehicle running. An engine target rotation number (Rr), which is obtained by converting the target vehicle speed pattern by values of the driving slip ratios (Sa), (Sb) and (Sc), is corrected for each of the running states. A new engine target rotation number obtained by this correction is used at the time of simulation, thereby controlling the rotation of the dynamometer.
According to another aspect of the first invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein a constant speed driving slip ratio (Sa) in a constant speed running state in a target vehicle speed pattern, an acceleration driving slip ratio (Sb) in an acceleration running state, and a deceleration driving slip ratio (Sc) in a deceleration running state are previously computed and stored as data for correcting tire slippage of the actual running vehicle. In each of the running states, the rotation number (Rta) {[Rta=RrX(1+Sa)], (Rtb) [Rtb=RrX(1+Sb)] or (Rtc) [Rtc=RrX(1+Sc)]}, which is obtained by adding to the engine target rotation number (Rr) a term obtained by multiplying the engine target rotation number (Rr) by the constant speed driving slip ratio (Sa), the acceleration driving slip ratio (Sb) or the deceleration driving slip ratio (Sc) is determined as a new rotation number subjected to a tire slip correction, and are used at the time of simulation, thereby controlling the rotation of the dynamometer.
The engine rotation pattern, which is obtained by converting from the target vehicle speed pattern in the conventional simulation, is shifted lower and higher than the engine rotation pattern of an actual vehicle running on a chassis dynamo. The present inventors have contemplated that this observation may be related to tire slippage. From this view point, a concept of introducing the driving slip ratio S was developed. The present inventors defined the driving slip ratio S using the average value of ratio between the engine rotation number shown by the engine rotation pattern and the engine rotation number shown by the engine rotation pattern. Further, since the engine rotation patterns are obtained from, for example, the target vehicle speed patterns including a constant speed (normal) section, an acceleration section and a deceleration section, each of states of constant speed, acceleration and deceleration can not be covered with one driving slip ratio S. From this point of view, the present inventors divided the driving slip ratio S into three kinds, i.e., constant speed, acceleration and deceleration, and respective slip ratios Sa, Sb and Sca were calculated.
The acceleration driving slip ratio Sb can be obtained in the following manner.
(1) Areas under acceleration curves A1 to A8 of the engine rotation pattern are obtained. For example, the area under the acceleration curve A1 is G1). These areas G1 to G8 are added. That is, G1+ . . . +G8 is determined as G.
(2) Areas under acceleration curves B1 to B8 in the engine rotation pattern are obtained. For example, the area under the acceleration curve B1 is R8 (shaded portion). These areas R1 to R8 are added. That is, R1+ . . . +R8 is determined as R.
Similar computations are conducted for all the deceleration curves C in the engine rotation pattern and all the deceleration curves D in the engine rotation pattern, thereby obtaining the slip ratio Sc.
The constant speed slip ratio Sa can be obtained by carrying out similar computations.
After the data is obtained to correct for tire slippage of an actual vehicle, the present inventors added, to the engine target rotation number (Rr), a term obtained by multiplying the engine target rotation number (Rr) by the constant speed driving slip ratio Sa, the acceleration driving slip ratio Sb or the deceleration driving slip ratio Sc. The result was determined as a new rotation number Rta, Rtb or Rtc after tire slippage is corrected for each of the constant speed section, the acceleration section and the deceleration section.
In the engine testing apparatus of the above structure, in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance which are taken into consideration in the conventional engine testing apparatus, the slippage between the tire and the road surface is also taken into consideration and therefore, it is possible to accurately reproduce the engine rotation during actual vehicle running.
The engine rotation pattern, which is converted from the new rotation numbers Rta, Rtb or Rtc and which correct for tire slippage, is not shifted from the measured engine rotation pattern. The engine testing apparatus of the present invention in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the new rotation numbers Rta, Rtb or Rtc, which correct for tire slippage, can carry out a simulation with high accuracy as compared with the conventional engine testing apparatus in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the target rotation number Rr.
Further, to achieve the above object, according to the second invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test, the dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein rotational acceleration of rotating bodies such as the engine, a transmission, a differential gear and a tire are obtained based on the target vehicle speed pattern. Each of the rotational accelerations are multiplied by an inertia moment of each of the rotation bodies to calculate a torque absorbed by each of the rotating bodies, and the engine under test is controlled such that the engine under test outputs a predetermined torque while taking these absorbed torque.
In the engine testing apparatus of the above structure, in addition to the inertia moment of the engine which is taken into consideration in the conventional engine testing apparatus, the inertia moment of other rotating bodies such as the transmission, the differential gear and the tire are also taken into consideration and therefore, it is possible to accurately reproduce the engine load during actual vehicle running, and to carry out a simulation with high accuracy.
To achieve the above object, according to the third invention, there is, provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test A driving slip ratio (y) is computed and stored as a multiple-degree equation function y=f(Tff) using, as a variable, an output torque (Tff) output from a torque generator and required by the engine. The engine target rotation number (Rr) is corrected using this value, and the rotation of the dynamometer is controlled using this corrected new rotation number.
According to another aspect of the third invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. Wherein a driving slip ratio (y) is computed as a multiple-degree equation function y=f(Tff) using, as a variable, an output torque (Tff) output from a torque generator and required by the engine, the rotation number (Rt) [Rt=Rr X(1+y)] obtained by adding, to the engine target rotation number (Rr), a term obtained by multiplying the engine target rotation number (Rr) by the driving slip ratio (y) is determined as a new rotation number after the tire slip correction is made, and the rotation of the dynamometer is controlled by using this new rotation number.
The present inventors considered that the reason why the engine rotation pattern obtained by converting from the target vehicle speed pattern in the conventional simulation is shifted lower and higher than the engine rotation pattern measured on a chassis dynamo is related to tire slippage. From this view point, a concept of the rotation correcting ratio during the actual vehicle running, such as, the driving slip ratio (y), was introduced. This is because it is defined that the driving slip ratio (y) during the actual vehicle running is determined as function of acceleration of the vehicle, and the acceleration of this vehicle can be simulated by converting into the output torque of the engine. That is, this is because the torque supplied to the tire from the engine through the transmission and the differential gear is transmitted to the road surface and becomes a driving force which accelerates the vehicle.
Thereupon, the tire slip ratio (y) is defined by the multiple degree function y=f(Tff) using the torque Tff for achieving the target output from the torque generator as variable.
The present inventors multiplied the engine target rotation number Rf (simply target rotation number, hereinafter) output from the rotation generator in the simulation by the driving slip ratio (y). The obtained tire slip correction term (Rr X y) is added to the target rotation number Rr, thereby making a new rotation number Rt which is corrected for the tire slippage.
In the engine testing apparatus of the above structure, in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance which are taken into consideration in the conventional engine testing apparatus, the slip between the tire and the road surface is also taken into consideration and therefore, it is possible to accurately reproduce the engine rotation of actual running vehicle.
As shown in FIG. 2, the engine rotation pattern 40, which is converted from the new rotation number Rt which is corrected for tire slippage, is not shifted from the measured engine rotation pattern, the engine testing apparatus of the present invention in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the new rotation number Rt which is corrected for tire slippage, can carry out a simulation with high accuracy as compared with the conventional engine testing apparatus in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the target rotation number Rr.